Power steering mechanism



Dec. 22, 1964 A. K. BROWN, JR 3,162,263

POWER STEERING MECHANISM Dec. 22, 1964 A. K. BROWN, JR 3,162,263

POWER STEERING MECHANISM Filed Sept. 24, 1962 3 Sheets-Sheet 2 4K1?" Mg', INVENTOR v ARTHUR K. RawMJR. BY

ATTafAff/ United States Patent Oli iz Patented Dee. 22, 1964 of Delaware Filed Sept. 24, 1962, Ser. No. 225,442 it) Claims. (Cl. 130--79.2)

This invention relates to power steering and more particularly to a novel compact rotary valve and worm gear power steering mechanism.

An object of this invention is to provide a conveniently small and mechanically simple power steering mechanism which is economical to `fabricate and is highly elhcient in operation.

Another object of this invention is to provide a power steering mechanism which utilizes approximately the same amount of space at the gear input as would a manual gear in this area.

A further object of this invention is to provide a compact power steering mechanism which utilizes a rotary valve of the type wherein the valve rotor is also a fail-safe input shaft which will permit positive means for manual steering in the event of power failure.

More speciically, it is an objectof this invention to provide a power steering mechanism wherein two oi the main components of the rotary valve, namely, the combination fail-safe input shaft and valve rotor, and the valve sleeve, each have one end thereof inserted tinto a hollow portion formed within a worm gear.

Another object of this invention is to provide a power steering mechanism wherein the combination input shaft and valve rotor is piloted within the worm gear.

A further object of this invention is to provide :a mechanical drive through pick-up means which provides a direct mechanical drive between the input shaft and the Worm in the event of power failure, but which will permit limited relative rotary motion between the input shaft and worm at all other times.

A still further object of this invention is to provide a power steering mechanism which, by virtue of the partial insertion of the valve sleeve and valve rotor within the worm, permits the elimination of one of the annular cylinder grooves in the valve sleeve.

Another object of this invention is to provide a power steering mechanism which utilizes a pressurized annular Teflon shoe between the valve sleeve and worm for providing a seal and preventing vibrations therebetween.

Au additional object of this invention is to provide in a power steering mechanism ot the type described a rotary valve porting arrangement which eliminates the necessity of returning luid to the outlet port via the bore in the valve rotor and eliminates iluid surges against the sleeve member tending to cause vibrations.

'The above and other objects and features of this invention will be apparent from the following description of the mechanism taken in connection with the accompanying drawings which form a part of this specification and in which:

FGURE l is a view, partially in section, of a power steering mechanism constructed in accordance with the present invention, which is shown in association with parts of a vehicle drawn schematically;

FIGURE 2 is a sectional View taken FlGURE l;

`FiCfURE 3 is a sectional view taken along line 3-3 of FIGURE 1;

FEGURE 4 is a sectional view taken along line 4 4 of FIGURE 1;

yFIGURE 5 is a composite sectional view which shows the passages of FIGURES 2,v 3, and 4 moved into the same along line 2--2 of plane for purposes of more clearly illustrating the ilow paths within the valve;

PEGURE 6 is a sectional View taken along line 6-6 of FIGURE 1; and

FIGURE 7 is a sectional view taken along line 7-7 of FIGURE 1.

Referring to FIGURE 1, it will be seen that reference numeral it) designates the front wheels of a vehicle to be steered by rotation of a steeiing shaft (not shown) which is suitably connected to input shaft 12. Operatively connected to the input shaft 12 is an hour glass worm i4 having a groove-type cam track 16 formed thereon and a stepped diameter bore 17 located within and at one end thereof which extends substantially to the bottom of the cam track without interfering therewith, said worm being held against axial displacement by radial thrust bearings 18 and i9 located at each end of the worm. A roller sector gear 29 is arranged to engage the cam track 16 of the worm and is carried by one end of a sector shaft 22 which is suitably journaled in gear housing 24. A pitman arm 2o is connected to the other end of sector shaft 22 and to the spindle Iarms 2d of the wheels I@ through a steering link-age assembly which includes tie rods 3Q, a cross tie rod S2, and a-n idler arm 34, suitably pivoted at one end to the Vehicle trame 36.

The hydraulic system of the power steering mechanism includes a fluid motor 33, which may be connected between the cross tie rod 32 and the vehicle frame 36, as shown in FGURE 1. However, the luid motor may be located at any other suitable position, e.g. integral with the steering gear housing. A piston 4t) divides cylinder i2 into opposed chambers constantly communicating -respectively with cylinder ports 44 and 46 of rotary valve 48, via conduits 50 and S2.

The main components of the rotary valve i8I yare the valve housing 54, the rotor 56 which is formed on the input shaft 12, and the sleeve 53 which is located between the rotor and valve housing. Located in the housing S4 are inlet port 6i?, outlet port 62, and the two previously mentioned cylinder ports 44E- and 46. It will be noted that the combination input shaft-valve rotor has one end thereof which rotates on needle roller bearing 64 which is located between the input shaft l2 and the valve housing 54 while the other end thereof extends into the bore portion 67 of stepped diameter bore 17 and rotates on a bronze bearing located between the 4input shaft and the worm ie. The rotor 56, contains six axially extending equally spaced slots formed on the outer periphery thereof, three of which are pressure slots and are designated by the reference numeral e8 and the other three of which are return slots and are designated by the reference numeral '79. lt will be noted that the return slots 7@ are longer than the pressure slots 68 so that the return slots may communicate with a return chamber 72 located at one end of sleeve S8. By utilizing long return slots 't which communicate directly with the return chamber 72 it is possible to eliminate the necessity for drilling radial holes into and out of the bore 74 of the rotor for achieving such communication and thereby also eliminate l'luid surges against sleeve 58 caused by such radial holes which tended to cause sleeve vibrations.

Located on the inner periphery of valve sleeve 53 are six axially extending equally spaced slots, three of which are designated by the reference numeral 76 and the other three of which are designated by the reference numeral '73. Formed on the outer periphery of valve sleeve 5S are three annulzulands Si), 82, and 24 and two annular grooves 28 and Qt). Since sleeve 58 extends into the bore portion 92 of `stepped diameter bore 17, it is possible to eiiminate the fourth annular land and third annular groove both of which are normally common to rotary valves of this general type, yas typified by Davis Patent No.

sible to communicate steering gear cavity 93 with sleeve slots 76 via radially extending passages 94 without the necessity for utilizingV an annular groove on the valve sleeve, since radially extending passages 94 open directly into the steering gear cavity. On the other hand, radially extending passages'96 communicate sleeve slots 78 with annular groove 88. Radially extending passagesr 98 cornmunicates rotor slots 68 with annular groove 90. Thus, it can be seen from the drawings, particularly FIGURES 1 and 5, that when the rotary valve 48, which is an open center'valve, is -in a neutral straight-ahead position, ow will occur from inlet port 60 to outlet port 62 via annular groove 90, radially extending sleeve passages 98, axially extending rotor slots 68, yaxially extending sleeve slots 76 and 78, axially extending rotor slots 70, `and re- A turn chamber 72. Cylinder port 44 communicates with sleeve slots 76 via radial sleeve passages 96 and annular groove 88, whereas cylinder port 46 communicates with sleeve lslots 76 via radial passages 94 and steering gear cavity 93. v

Seals are located in annular lands S0, 82, and 84 to prevent leakage thereacross. These seals are glass filled Teflon endless sealing rings of rectangular section. The glass content increases pressure which can be tolerated prior to extrusion and only slightly increases friction compared to pure Teoni The glass iilling is 15% ground fibers by weight. Higher percentages of glass reduce the ability of this material to stretch in addition to increasing the coeicient of frictionv of the material in contact with metals. Stop-off rings 105 seal off the axially extending sleeve slots'76 and 78 and also serveV as bearings. f

In order to prevent possible vibrations between the valve sleeve 58 and worm 14, an annular Teflon shoe 107 is interposed therebetween and is pressurized by .fluid communicated thereto from one of said axially extending pressure slots 68 via a passage 109. Such pressurization causes the Teflon shoes to expand radially. Y

An eccentric screw 104, as shown in FIGURES 1 andy 7, is used to key the valve sleeve 58 directly to the worm. The eccentric screw is threadedinto the worm at one end 106 and hasthe other spherical head'end 108 extending into and in contact with the wall of a close fitting cylindrical hole 110, said hole vbeing drillled into the end of valve sleeve 5S. After removing the'threadedV at one end 11510 the input rotorv land at the other end 116 to the worm, thi-s adjustment also rotates Vthe sleeve Y with respect to the rotor thereby permitting balancing ofthe pressures on opposite sides of piston 40.

The three equally spacedl ow paths previouslyV de scribed give balanced forces within the vallve due to uid f How, thereby eliminating any stickiness due to hydraulic unbalance. Upon rotation ofthe steering wheel the valve rotor 56 is rotated relative to the valve sleeve 58 as a result of deection of the torsion rod 114 which connects thevalve rotor andthe steering gear worm. This movement is in proportion to input torque. As can more clearly be seen by reference'to FIGURE 5, relative rotation between valve rotor 56 and valve sleeve 58 will cause one of the cylinder Vports 44, 46 to communicate"VVV with the inlet port 60 andthe other cylinder port to communicatewith the outlet port 62. vThis will create a "dierential pressure across piston and will result in power assisted steering.

V1t win be geen 'from FIGURES 1 ande that a mechanical drive through pick upconnection 117 is provided-be,-

failure. At all other times this connection will .permit limited relative rotary motion between the input shaft land the worm. More specifically, the mechanical drive through connection includes an internal yspline 118 formed in the stepped diameter bore 17 of the worm yand an internal loose fitting spline 120 on the end of the input shaft extending into the stepped diameter bore. It will be noted that suicient clearance is provided between the internal and external splines for normal valve movement. If, however, power failure occurs, the driver will .deflect the torsion rod'until contact is made between the splines. Inputtorque is then transmitted exactly as in la manual steering system. The torsion rod 114, which connects the valve rotor 'and worm, provides mechanical feel without preventing the necessary angular movement required between the sleeve and rotor for valve Y operation.

Vit will be obvious to those skilled in the art that various changes may be made inthe form, structure, and arrangement of parts without departing from the spirit of the invention. Accordingly, 'applicant does not desire to be limited to the specific embodiment disclosed herein primarily for purposes of illustration, but instead desires protection falling within the scope of the appended claims.

Having thus Vdescribed the various features of the invention, what I claim as new and desire to secure by Letters Patent is:

l. In a power steering mechanism including ,an input member, van output member, and a fluid motor operatively connected to said output member, the combination Within fa housing, of a worm having'grooves means formed thereon and a stepped diameter bore located Within and at one end thereof which extends substantially to the bottom of said groove means without interfering therewith follower means operatively connected to said output member and engaging said groove means, a pair of relatively rotatable telescoped tubular elements through which fluid flow to and from said motor is controlled, one of which is a part of `said input member and the other of which is connected to said worm, said tubular elements each having oney end thereof extending into andlocated substantially within said steppedvdiameter bore' Vof said worm,

'and mechanical drive through pick-up means located on one end of said input member :and in said stepped diameter bore` of said worm for permitting limited relative rotary motion between said input member and said worm.

tween the combination input rotor 12, 56 and the worm Y 14, which vwill result in a direct mechanical drive between the input shaftiandthe worm in4V the event of power-- 2. In a power steering'mechanism including an input member, an output member, and a uid motor operati-velyconnected to'said 'output member for applying thereto, thecombination `withinra housing', of an hour glassworm having a cam track thereon and a stepped diameter bore locatedwithin and at one end' thereof which extends substantially to the bottom of the cam track without interfering'- therewith, a follower operatively connected to said output member Aand engaging said canttrack, a pair 'of relatively rotatable telescoped Vtubular elements through which uid iiow to and from said motor is controlled,one'of which is said input memv ber kand the other of which is a sleeve member connected to said hour glassy wormand'located between said input memberand saidhousing,` said tubular elements each 'having one end4 thereof extending into V,and locatedy substantially' within said stepped diameter bore of usaid hour glassworm, and mechanical-drive through pick-up means located on said one en'd of Vsaid input member and in said lstepped diameter bore ,of said. hour glass worm for permitting limited relative.rotary motion between said input member and said worm.

3. A power steering mechanism, as dened in claim 2, wherein said mechanical drive through pick-up means includes an internal spline formed in the stepped diameter bore of said hour glass worm and an external loose fitting spline formed on said one end of the input member.

4. A power steering mechanism, as defined in claim 2, wherein a sleeve-type bearing is interposed between said one end of the input member and the stepped diameter bore of said hour glass worm.

5. In a power steering mechanism including an input member, an output member, and a Huid motor operatively connected to said output member for applying power thereto, the combination within a housing, of an hour glass worm having a cam track thereon and a stepped diameter bore located within and at one end thereof which extends substantially to the bottom of the cam track without interfering therewith, a follower operatively connected to said output member and engaging said cam track, a pair of relatively rotatable telescoped tubular elements through which iiuid ow to and from said motor is controlled, one of which is said input member and the other of which is a sleeve member connected to said hour glass worm and located between said input member and said housing, said tubular elements each having one end thereof extending into and located substantially within said stepped diameter bore of said hour glass worm, a plurality of axially extending slots formed on the outer periphery of said input member and the inner periphery of said sleeve member, said slots being in overlapping relation when said input and sleeve members are in a neutral position, inlet, outlet and two cylinder ports located in said housing, inlet passage means located in said sleeve member for communicating half of the slots on said input member with said inlet port, outlet passage means located at the end of the sleeve member furthest removed from said worm for communicating the other half of the slots on said input member with said outlet port, two cylinder passage means located in said sleeve member, one of which communicates, half of the slots in said sleeve member with one of said cylinder ports and the other of which communicates the other half of said slots in said sleeve member with the other of said cylinder ports, and mechanical drive through pick-up means located on said one end of said input member and in said stepped diameter bore of said hour glass worm for permitting limited relative rotary motion between said input member and said worm.

6. In a power steering mechanism including an input member, an output member, and a fluid motor operatively connected to said output member for applying power thereto, the combination of a housing having a valve bore and a steering gear cavity therein, an inlet, outlet and two cylinder ports located in said housing, an hour glass worm having a cam track thereon and a stepped diameter bore located within and at one end thereof which extends substantially to the bottom of the cam track without interfering therewith, a `follower operatively connected to said output member and engaging said cam track, said hour glass worm and follower being located in the steering gear cavity of said housing, a pair of relatively rotatable nested tubular elements through which fluid iiow to and from said motor is controlled, said tubular elements being located in the valve bore of said housing, one of said elements being said input member and the other of said elements being a sleeve member connected to said hour glass worm and located between said input member and housing, said tubular elements each having one end thereof extending into and located substantially within said stepped diameter bore of said hour glass worm, means for opposing rotation of said input member, only two annular grooves formed on the outer periphery of said sleeve member and defined by three annular lands each having sealing means in contact with said valve bore, passage means for communicating one of said outer annular grooves with said inlet port and the other of said annular grooves with one of said cylinder ports, a plurality of axially extending slots formed on the inner periphery of said sleeve member and the outer periphery of said input member, said slots being in overlapping relation when said input member and sleeve are in a neutral position, inlet passage means located in said sleeve member for communicating half of the slots in said input member with said inlet port via one of said annular grooves, outlet passage means located at the end of the sleeve member furthest removed from said worm for communicating the other half of the slots in said input member with said outlet port, first cylinder passage means located in said sleeve member for communicating half of the slots in said sleeve member with one of the cylinder ports via the other of the outer annular grooves, second cylinder passage means located in said sleeve member for communicating the other half of said slots in said sleeve member with the other of said cylinder port via said steering gear cavity, and mechanical drive through pick-up means located on said one end of said input member and in said stepped diameter bore of said hour glass worm for permitting limited relative rotary motion between said input member and said worm.

7. A power steering mechanism, as defined in claim 6, wherein resilient means are located between said sleeve member and the stepped bore of said hour glass worm for providing a seal and preventing vibrations therebetween.

8. A power steering mechanism, as dened in claim 7, wherein said resilient means includes an annular Tellen shoe which is caused to expand radially by liuid pressure communicated thereto from said inlet port.

9. A power steering mechanism, as defined in claim 6, wherein said means for opposing rotation of said input member includes a torsion bar having one end thereof rigidly connected to said input member and the other end thereof rigidly connected to said hour glass Worm.

10. A power steering mechanism, as defined in claim 6, wherein the slots on said input member which communicate with said outlet port via said outlet passage means are longer than the slots on said input member which communicate with said inlet port via one of said annular grooves, said longer slots being arranged to permit a direct communication with said outlet port and thereby obviate fluid surges against said sleeve member tending to cause vibrations.

References Cited in the tile of this patent UNITED STATES PATENTS Hammond Nov. 29, 1955 

1. IN A POWER STEERING MECHANISM INCLUDING AN INPUT MEMBER, AN OUTPUT MEMBER, AND A FLUID MOTOR OPERATIVELY CONNECTED TO SAID OUTPUT MEMBER, THE COMBINATION WITHIN A HOUSING, OF A WORM HAVING GROOVES MEANS FORMED THEREON AND A STEPPED DIAMETER BORE LOCATED WITHIN AND AT ONE END THEREOF WHICH EXTENDS SUBSTANTIALLY TO THE BOTTOM OF SAID GROOVE MEANS WITHOUT INTERFERING THEREWITH FOLLOWER MEANS OPERATIVELY CONNECTED TO SAID OUTPUT MEMBER AND ENGAGING SAID GROOVE MEANS, A PAIR OF RELATIVELY ROTATABLE TELESCOPED TUBULAR ELEMENTS THROUGH WHICH FLUID FLOW TO AND FROM SAID MOTOR IS CONTROLLED, ONE OF WHICH IS A PART OF SAID INPUT MEMBER AND THE OTHER OF WHICH IS CONNECTED TO SAID WORM, SAID TUBULAR ELEMENTS EACH HAVING ONE END THEREOF EXTENDING INTO AND LOCATED SUBSTANTIALLY WITHIN SAID STEPPED DIAMETER BORE OF SAID WORM, AND MECHANICAL DRIVE THROUGH PICK-UP MEANS LOCATED ON ONE END OF SAID INPUT MEMBER AND IN SAID STEPPED DIAMETER BORE OF SAID WORM FOR PERMITTING LIMITED RELATIVE ROTARY MOTION BETWEEN SAID INPUT MEMBER AND SAID WORM. 